In EEG studies on sleep and dreaming no attention has been given to hemispheric asymmetry in the EEGs characterizing the stages of sleep, or to the possibility that the two hemispheres make different contributions to the mental activity of sleep. Several clinical reports lead us to the hypothesis that the right hemisphere is more actively engaged in dream cognition than is the left. We have been studying the specialization of the cerebral hemispheres for different waking cognitive functions; the left for verbal-analytical processes and the right for processes involving patterns and holistic perceptions (e.g., spatial relations). By studying EEG asymmetry we have been able to distinguish verbal from spatial processing as it occurs in normal subjects. During verbal tasks the alpha power in the left hemisphere is less than in the right, and during spatial tasks the alpha power in the right hemisphere is less than in the left. We propose to look for EEG asymmetry in REM sleep, and hypothesize that the asymmetry will be similar to that seen in the waking state during tasks which primarily engage the right hemisphere. Furthermore, we would expect that the variation in the quality of non-REM mental activity from logical thought to bizarre vivid imagery may be associated with similar variations in EEG asymmetry. Recordings will be made from P3, P4, T3, and T4 in each stage of sleep, for four nights, and in the waking state during the performance of tasks which engage primarily the left hemisphere (Writing from Memory) or the right hemisphere (Block Design Test). Power spectral analysis and ratios of right to left power will be computed for each state. We will examine the sleep records to determine whether the different stages show characteristic asymmetries, and if so, whether they resemble the waking asymmetries associated with performance of verbal-analytic or spatial-holistic tasks. If this part of the project is successful we will investigate the relationship of EEG asymmetry to the content of reports when the subjects are awakened in the different stages of sleep.